Determination of benzene polycarboxylic acids in atmospheric aerosols and vehicular emissions by liquid chromatography-mass spectrometry

Abstract

A simple, sensitive and reliable LC-ESI(−)/MS method was developed for determination of selected aromatic dicarboxylic acids (e.g. phthalic acid isomers) and tricarboxylic acids (e.g. trimellitic, trimesic) in atmospheric aerosols and vehicular emissions without complex sample pre-treatment. Gradient liquid chromatographic separation was performed on a Zorbax SB-Aq (150 × 2.1 mm i.d., 3.5 µm) column using a mobile phase consisting of 0.1% formic acid (eluent A) and methanol (eluent B). The Zorbax SB-Aq column was chosen as it was specifically designed to retain highly polar compounds, allowing the use of highly aqueous mobile phases. The method was demonstrated to be sensitive and precise. In the SIM mode, LODs for all target acids dissolved in double deionized water were in the range of 0.03–0.1 µg/L. The method showed a good inter-day precision of retention time (RSD <0.3%) and peak area (RSD <3%). Satisfactory recoveries, ranging from 89 to 107% for the spiked blanks and extracts of real samples, were obtained. The method has been successfully applied to the quantitative analysis of selected benzene polycarboxylic acids in urban atmospheric aerosols and particulate matter emitted from diesel- and gasoline-powered motors. Preliminary results suggest that 3-hydroxyphthalic acid may be used as a potential tracer for diesel engine emissions.